Background/Purpose: According to the ASAS classification criteria for axial spondyloarthritis (SpA), the presence of structure changes of sacroiliac (SI) joints such as sclerosis, bone erosion, joint space widening or ankyloses can’t be adopted to confirm active sacroiliitis on magnetic resonance imaging (MRI) in the absence of bone marrow edema (BME). Previous data indicated less than half Asian patients with axial SpA were characterized by BME. For patients with early phase of SpA, HLA-B27 is associated with early diagnosis and axial inflammation of SI joints on MRI, while serum c reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are incapable of predicting early sacroiliitis. Nonetheless, HLA-B27 is not associated with structural lesions of SI joints. All factors contribute to difficult defining early Asian SpA patients in the absence of serum HLA-B27 and obvious imaging inflammation. This study aims to define the prevalence of structure changes of SI joints on MRI in Taiwanese patients with non-radiographic axial SpA and identify how to confirm an early diagnosis of HLA-B27 negative axial spondyloarthritis.

Methods: Eighty patients with inflammatory back pain and morning stiffness and high disease activity (BASDAI≥4) who had to be either serum HLA-B27 positive (27 patients) with ≥1 SpA-feature or HLA-B27 negative with ≥2 SpA-features (53 patients) were included in this prospective study. All patients were tested for X-rays of the pelvis before MRI examination and did not meet the definition for a positive radiograph according to the modified New York criteria. MRI of sacroiliac joints (MRI-SIJ) was performed with multiple sequence (Coronal and axial T1-weighted spin echo, coronal and axial short-tau inversion recovery). SI joints were evaluated for the prevalence of subchondral BME and structure changes, including sclerosis, bone erosion, joint space widening and ankylosis. All MRI-SIJ were scored according to the SPARCC score. All patients were tested for serum levels of ESR and CRP. Correlation analysis was performed among the different collected variables.

Results: Subchondral BME was present in 12 of 57 patients with HLA-B27 serum negative SpA (21.1 %), while 15 of 23 (65.2 %) HLA-B27 serum positive SpA patients had active BME on MRI (p = 0.02). Patients with SpA and positive HLA-B27 were characterized by higher SPARCC scores, compared to serum negative patients (p < 0.001). Structural changes of SIJ, including sclerosis, bone erosion and joint space widening were identified in 20 (86.9 %), 27 (100 %) and 10 (43.5 %) SpA patients with positive HLA-B27, respectively. These structural changes of SIJ on MRI were less common in HLA-B27 serum negative patients, as 30 (52.6 %), 50 (87.7 %) and 9 (15.8 %) of 23 patients, respectively. Among patients with high serum ESR or CRP, joint space widening developed accompanied with higher SPARCC scores (p = 0.024 and 0.019, respectively).

Conclusion: MRI is able to detect active sacroiliitis and structure changes of SI joints for patients with non-radiographic axial spondyloarthritis in the absence of serum HLA-B27. Structure changes on MRI-SIJ could be used alternatively for early diagnosis of SpA in Asian people whom are characteristic by less bone marrow edema.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/mri-contributes-to-accurate-and-early-diagnosis-of-non-radiographic-hla-b27-negative-axial-spondyloarthritis/